Demonstration of a gradient in inhibin activity, estrogen, progesterone, and delta 4-androstenedione in follicular fluid, ovarian vein blood, and peripheral blood of normal women

Inhibin assays of ovarian cyst liquid obtained by needle aspiration may allow differential diagnosis between functional and organic cysts

Radioimmunoassays of estradiol, CA125 and inhibin were carried out on ovarian cyst fluid samples. The samples were taken from ten women with functional cysts and 15 women with organic cysts. Statistical analysis shows that estradiol and inhibin assays allows satisfactory differential diagnosis between functional and organic cysts. However, the inhibin assay provides more precise results and appears to be a more reliable marker than estradiol. The differential diagnosis between the two types of cyst would indicate the use of coelioscopic surgery especially in the case of organic cysts, avoiding unnecessary risks for patients with functional cysts.

The maternal ovary is not the source of circulating inhibin levels during human pregnancy

The concentration of immunoreactive inhibin in serum was measured in three pregnant women with premature ovarian failure involved in a donor oocyte in-vitro fertilization programme. Inhibin was not detectable in peripheral serum prior to conception but rose within 2-4 weeks of embryo transfer, whereafter levels rose gradually during pregnancy (less than 20 weeks 1.22 U/ml (0.85-1.76) versus greater than 20 weeks 2.28 U/ml (1.42-3.67), P less than 0.01; geometric mean +/- 67% confidence interval) and were similar to those observed in 24 normal pregnant women. hCG rose in parallel with inhibin during early gestation, but declined after 3 months. FSH levels were elevated before conception and were suppressed during pregnancy. In conclusion (i) immunoreactive inhibin is detectable from early gestation in women with no endogenous ovarian function indicating that the maternal ovary does not contribute significantly to inhibin secretion during pregnancy; (ii) the trophoblast is the likely source of inhibin during pregnancy; (iii) the regulation of hCG and inhibin secretion differs throughout gestation; and (iv) inhibin may have a role in FSH regulation during pregnancy and/or a local role within the feto-placental unit.

Inhibin A-subunit gene expression in the ovaries of immature female rats is stimulated by pregnant mare serum gonadotrophin

We have used a bovine cDNA probe for the A-subunit of inhibin to demonstrate the presence of inhibin in the ovaries of immature female rats: the levels of mRNA were increased following treatment of the rats with pregnant mare serum gonadotrophin (PMSG), suggesting modulation by PMSG of ovarian inhibin synthesis at least at the level of transcription. Furthermore, we report the unexpected finding of significant levels of inhibin mRNA in the corpora lutea of mature female rats. No inhibin mRNA was demonstrable in the uterus or placenta.